65-2646XL-05-04 M2A Transmitter Operator’s Manual
Chapter 8: RS-485 Modbus Output
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Supported Modbus Functions
The M2A supports Function Code 03: Read Holding Registers and Function Code 16: Write
Registers.
Function Code 03: Read Holding Registers
There are a total of 40 registers available to be read via this Function Code.
Registers 1 - 2
The format (bit & field assignments) for registers 1 - 2 is shown below in Table 10 - Table 11.
Table 10: Register 1, Numerical Reading with Sign & Decimal Point Bit & Field Assignments
Bit(s)
Value & Field
[15]
Sign of Reading
0 = Positive
1 = Negative
[14:13]
Format of Reading
0 = XXX (no decimal point)
1 = XX.X
2 = X.XX
3 = .XXX
[12:0]
Numerical value of display reading (8000
max)
Table 11: Register 2, Operating State, Alarms & Relays Bit & Field Assignments
Bit(s)
Value
[15:12]
Operating State
0 = Undefined
1 = Initialization
2 = Normal
3 = Warm-up
4 = Fail
5 = Calibration
6 = Post-Calibration
7 = Low Power
8 = Setup
[11]
Gas Type Change
0=Not Changed
1=Changed
